With the development of the display technology, various display devices have been widely used. The mainstream of the display devices may include: thin film transistor liquid crystal display (TFT-LCD), Active Matrix Organic Light Emitting Diode (AMOLED), and the like.
In the manufacturing processes of various display devices, various structures need to be formed on the substrate. For example, films are deposited on the substrate, and then a patterning process is performed on the films to form various patterns; or only depositing films on the substrate to form film layers. Here, the patterning process may include processes such as photo resist coating, exposure, developing, etching, photo resist stripping, and the like.
In depositing a film and performing a patterning process, substrate shift, mask shift in the exposure process, and etching time variation in the etching process all can result in a variation in distance between the edge of the film and the edge of the substrate. There is no technical solution that can detect the film edge in the prior art, which results in that the variation in the distance between the edge of the film and the edge of the substrate may not be detected in time, thus reducing the yield of the production and increasing the production loss.